Vertical Fluctuations of Key Parameters of the Self-Purification in the “Middle Iskar” Cascade’s Reservoir Lakatnik

Sofia University “St. Kliment Ohridski”, Departament of General and Applied Hydrobiology, Faculty of Biology, BG – 1164 Sofia, Bulgaria


YOTINOV, I., S. LINCHEVA and Y. TOPALOVA, 2014. Vertical fl uctuations of key parameters of the self-purifi - cation in the “Middle Iskar” cascade’s reservoir Lakatnik. Bulg. J. Agric. Sci., Supplement 1: 113–117


Iskar River is a highly modifi ed ecosystem in the part Prokopanik-Gabrovnitza from the newly built small Hydroelectric Power Plants (HEPPs) in the “Middle Iskar” cascade. A 12-year monitoring program studies the ecological status of the river and gradually under construction, putting into operation the HEPPs and associated dams. This article covers the period when the one dam at HEPP Lakatnik were constructed and started its exploitation. The aim is to determine the infl uence of the vertical fl uctuations of the key hydrochemical and microbiological indicators of the water column on the self-purifi cation processes. On the base of these parameters the assessment of infl uence of technological exploitation, morphology and depth of water column on biotransformation processes has been made. An additional valuable information for the connection of self-purifi cation potential and synchronize functioning of reservoir has been extracted by means of our results. In the micro-dam Lakatnik microbiological (aerobic heterotrophic bacteria and endo-bacteria) and hydrochemical parameters (content of nitrate, nitrite, ammonium and phosphate ions, chemical oxygen demand, content of oxygen, dissolved and unsoluble suspended solids, total dry weight) were investigated in the following water horizons: Lakatnik – 0, –1, –2.5 and –3.5 m. The used methods were according to the Bulgarian State Standards, therefore, our results are oriented to an assessment of the water quality in correspondence with existing regulations. These results indicate that the available local fl uctuations are not signifi cant. All data are in compliance with the existing ecological, hydrological and technological features of the studied water bodies, which plays an important role for the following: 1) Discovering of mechanisms and possibilities for increasing the effi ciency and effectiveness of the monitoring strategy; 2) An adequate decision-making process in the technological exploitation of the Middle Iskar cascade.

Key words: Middle Iskar cascade, reservoirs, microbiological and hydrochemical indicators, depth fl uctuations, self-purifi cation
Abbreviations: AeH – aerobic heterotrophic bacteria, COD – chemical oxygen demand, DSS – Dissolved Suspended Solids, Endo – endo-bacteria, HEPP – hydro electric power plant, TSS – total suspended solids, USS – Unsoluble Suspended Solids


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